Screening mechanism



Dec. 7, 1954 R, MILLER 'ETAL 2,696,302

SCREENING MECHANISM Original Filed Sept. 10, 1949 L- I 6/ I f3.9-. z 37 I I15; I 29 F El I I I ,7 A 6/" m 28 24 I m I I8 23 E M 27 22 I 2/ M l6 5 I I? i I I 2 j n 22 l Halal. IO

54 ROBERT P. MILLER FRANK MATHEWSON N J 3/ (3-H. MEINZER ATTORNEY IGI4 59 r 6 p F INVENTORS /aML U.

United States Patent SCREENING MECHANISM,

Original application September 10, 1949, Serial No. 114,966. Divided and this application January 25, Y 1952, Serial No. 268,311-

3 Claims. (Cl. 209-332) This application is a division of our copending application Serial No. 114,966, filed September 10, 1949, and entitled Screening Mechanism.

I This invention relates to apparatus for separating granular and pulverulent solid materials into desired size ranges by passage over and through foraminous media sllich as wire mesh screens, plastic screen cloth and the 1' e.

The invention is illustrated herein as embodied in a screening apparatus of the type described in United States Patent 2,284,671 entitled 1942, to G. H. Meinzer, in which the screening element is subjected to a gyratory motion in a substantially horizontal plane and simultaneously to progress tilting around its own center, reference being made to the said patent for a full description of the basic elements of the structure and the manner in which the described gyratory and tilting movements are produced.

Broadly described, the combination to which the present invention pertains includes a cylindrical frame spanned by a screen, this cylindrical frame with its screen being mounted in a floating manner by suitable support springs on a lower sub-frame. The floating structure, i. e., the upper cylindrical frame, carries on its under side a suitable motor, the motor shaft being upright and carrying an upper unbalanced weight above the motor and a lower unbalanced weight below the motor. It is oscillation of these two eccentric weights that produces the desired gyratory and tilting movements of the floating structure.

Since both the eccentric weights and the motor are suspended'from the floating upper cylindrical frame and since-these'components far outweigh the rest of the floating structure, it is difficult to keep the center of gravity of the floating structure'from being too low. If the center of gravity is elevated to the plane of the upper eccentric weight, the oscillatory movement of the floating structure will pivot about the center of gravity in that plane in a highly desirable manner. Moreover the closer the pivot center of oscillation to the screen across the upper cylindrical frame, the less the vibratory stress imposed on the screen.

It is an object of the present invention to elevate the center of gravity of the floating structure including the motor and weights and to minimize the vertical distance of the center of gravity from the screen carried by the upper cylindrical frame. A further object is to provide an eflicient bottom structure for the upper cylindrical frame to carry the weight of the suspended motor and eccentric weights.

In general these objects are attained by providing the upper cylindrical frame with a re-entrant bottom wall to provide a space for the upper eccentric weights that is at a relatively high level. Rigidity in the mounting of the motor on the underside of the upper cylindrical frame is important because any flexure on the part of the structure between the eccentric weights and-the screen carried by the upper cylindrical frame will not only introduce distortion of the generated pattern of motion, but will also result in fatigue of the support structure. It is apparent that rigidity is paramount and that the rigidity of the bottom structure may be enhanced by a re-entrant configuration for the bottom wall of the cylindrical frame. A conical configuration is preferred.

The advantages of the invention will become evident on inspection of the attached drawings and the following description thereof, in which Shaking Device, issued June 2,-

Patented Dec. 7, 1954 1 is a vertical section on the center line of the asshowing the motor and counterweights the clamping ring shown in Fig. sembled apparatus, in elevation and omitting Fig. 4;

Fig. 2 is a cross section through the subframe A, as on the line 2-2 of Fig. 1;

Fig. 3 is a cross section through the screen-supportlng section B, showing certain underlying members in plan, as on the line 3--3 of Fig. 1;

Fig. 4 is a sectional detail through the outer edge of the screen cloth and the rings between which the cloth isretained, showing also the manner of assembling superposed screen frames.

Referring first to Figs. element or subframe A of the. machine consists of a cylinder 10 of steel plate provided with angle iron flanges 11 and 12 at its lower and upper ends. The lower flange should have several bolt holes 13 for attachment of the subframe to a floor or foundation. As almost no vibration is transmitted to the subframewhen the machine is in operation and there is little or no tendency to walk, the foundation of whatever kind need only be sufficient to ciarry the dead weight of the machine and its operating 0a The upper flange carries a plurality of open coil springs 14, preferably four in number, interposed between the subframe and the screen-carrying frame B. These springs support the screens, motor and other moving parts of the apparatus and permit the screens to gyrate and tilt in the manner described in the Meinzer patent. Generally speaking, the stiffness of the springs should be such that they will be only slightly deflected, in a closing direction, by the dead weight of the supported parts of the mechanism'when empty, and only partially closed by the dead weight of these parts when loaded. The lower ends of these springs are rigidly affixed to the upper flange as by bolts 15.

The supporting section B consists of a short steel plate cylinder 16 within which is welded a truncated, relatively flat, steel plate cone 17 which in turn carries a motor housing 18. Radial plates 19 stiffen this structure and prevent vibration of the housing with respect to the cone. A vertical electric motor 20 is supported within the housing on internally projecting rings 21 and 22, the motor being locked. in position as, for example, by means of conical wedges 23 and drawbolts 24. Electrical connections may be made to the motor in any convenient manner, as for example through a freely flexible conduit 25 passing through bushings 26 and 27 in the walls of the subframe and housing. The upper ends of springs 14 are bolted to stirrups 28 projected from the lower face of cone 17. A shield plate 29, slightly dished upwardly, is removably bolted over the upper end of the motor housing, and a tension bolt 30 is projected upwardly from the center of the plate. The upper end of cylinder 15 is providedwith a flange 31 to which the stack of screen frames is attached as will be described.

The motor 20 is provided, as in the Meinzer patent, with unbalanced weights 32 and 33, attached respectively to the upper and lower ends of the motor shaft 33' in such manner that their radial angle may be varied. Either or both of these weights may also be varied in magnitude, the upper most conveniently by substituting one weight for another, the lower by attachment or removal of bolted-on weights 34.

The stack resting on the upper flange 31 of the supporting section may consist of any required number of screens, reserving that it is undesirable to make the stack so high as to be top heavy. If but two fractions are to be made (one over and one through) only one screen frame will be required, this being the upper frame D. If a greater number of separations are to be made, one or more intermediate frames C must be provided.

The form indicated at D, which in any case will be the uppermost of the stack, is a short cylinder of steel plate having an upper flange 31 and a lower end flange 35. The form indicated at C, which will be used. in any intermediate position, has an upper end flange 31", a lower flange 35', together with a feed return pan 36 and means later described for protecting the periphery of the screen cloth against damage.

1 to 3 inclusive, the lowermost The feed return pan, the purpose of'which is to collect the undersize passing through the" screen next" above and* direct it to the center of the screen next below, is a shallow cone of light sheet metal having a central opening-37L Over this opening is pl'acedaspider: 38 having acentralboss 39 from which= a tensiontboltflflf"isrdirected upwardly.

The screen cloth 40 is mounted in a circular frame: comaposedof twofiat metallic: rings 4]; and 42: (see: E1g.4 and narrow rings 43 and 44 of rubberor other elastic: material interposedbetween. the screen. clothrandi the inner edgesof the metallic. rings; Beforernounting,v the: cloth is stretched evenly in both: directions, in'any' Q9113" venient manner, until it. lies flat and smooth,,afterrwl :nch the above described. rings are applied onv opposite sides, the outer. edges of the metallic: rings. are: brought. into: close contact with the cloth, and these edgesvare spot welded to the cloth and toeach-other. as; at 41",. after which projectingv portions of. the cloth. are trimmed away, leavinga circle of screencloth. enclosedi in a stiff? metallic ring in whichit is held under such: tension as was imparted in the original stretch. The advance: preparation of the screen cloth element as above described. greatly facilitates the changing. of screens. and the. assembling of a. screen stack.

At the center of the screen cloth a hole iszpunch'ed of such size as to pass over tension bolt 30 so thatalsuitable; nut may be threaded onto the bolt to pull the screen taut inxa; downward direction. Surrounding. this; opening and on opposite sides of thescreen are placed suitablernetal. 9

washers to receive the bolt. as. shown. in Fig;v 1. The inner edgesv of the metallic. washers are welded or brazed. to. the screenand to each other.

In the. operation of a screen having. the combined gyratory and tilting motion described in' the; Meinzer patent, the forces which. produce movement; of: the. feed over the surface of the cloth. act. tangentially with the. result that a particle whichtremains on therupper surface of the cloth moves in a; constantly wideningspi'ral. until it encounters. the enclosingwall, around which: it travels until it escapes through a delivery spout 61 communicat ing with an openingv through the wall.. This tendency to travel toward the edge of. the cloth i's'resistedzby directing the cone of the screen cloth downwardly, thefeed. being. thus forced. to travel uphill to escape. A highly useful control. of time of retention of. the oversize on any given screen, under fixecl'conditions of rapidity and. magnitude of. gyration, may be exercised by varying the:sl0pe of the screen cone, an: increase in slope: increasing retentionu This control. may be utilized to increase the. throughput:

capacity of the screen or to improve; the: sharpness: of separation between oversizeand undersize.

Because the feed travels outwardly over' the. screen, maximum utilization of. the surface depends: on feeding cachscreen centrally. The uppermost screen of the: stack 1s fedin this location through any feed spout-(not shown) while the return of the: undersize'from one: screen to the center of the screen next'below is etfectedby conicalapans 36, the slope of which must be: suflicient to cause-gravita tion to overcome the tendency of gyration to cause: thesolids to move outwardly.

As canv be understood by referencento Fig. 1;,the upper screen of which is assumed to be fed centrally, the oversize from screen 40 passes out through delivery spout 61, the undersize falling onto pair 36 and passing by gravity' to central opening 37 and through it onto screen 40' of the next finer mesh. The oversize from screen 40 passes out through spout 61' and, as this is the last screen in the stack illustrated, the undersize falls onto shield 29 and cone 17 and passes out through spout 61".

We claim as our invention:

1... In=screening mechanism of the type in which. rotationinsubstantially horizontal. planes of apair of'spaced, unbalanced weights imparts motion to a. horizontally disposed screening member: an upright subframe; a cylindrical frame above said subframe; a partition member extending across said cylindrical frame and united therewith, said partition being in the form of a cone with its apex uppermost and with its lower periphery positioned generally horizontally; a plurality of open coil springs in compression between said partition member and said subframefor resilient support. of the partition member together. with the cylindrical frame; a motor spaced. below said partition member, said. motor:- being rigidly con.- nected to the underside thereof; a shaft extending upward from said motor towards said. partition member; unbalan'cedsweightsaon said shaft inside the. conical configuration of said partition: member above: the plane of the periphery of the partition member; and a screen cloth extending. across said cylindrical frame above said partitionmember, there being an opening adjacent. the periphery-of'said screen: cloth: for the continuous discharge of material too large for the: mesh of the screen cloth and opening, near the periphery of said partition. member for the. continuous discharge. of material: that passes through said screen cloth.

2.. A screening. mechanism. as set forth in claim 1 which: includes. means. extending. upward from i said partition member to draw the central portion ofsaid screen cloth: downward to form'the screen. cloth: into. a shallow cone.

3'... Inscreening mechanism. of the. type in which substantially: horizontal rotation of unbalanced Weight imparts. motion to a substantially horizontally disposedi screen: a subframe;a screen-carrying frame; coil springs resiliently supporting the screen-carryin'gzframe. above thesubfram'e; a partition connected to and extending across the screen-carrying frame; a. motor rigidly supported by the screen-carrying: frame. below thepartition; a shaft extending: upwardly from. the motor; an unbalanced weight on: said. shaft, said partitions being. upwardly inclined toward: itscenter tov provide. space for said weight; and a. screen connected toandextending across. the screencarrying-1 frame: above the. partition, said screen-carrying frame having an. opening. for dischargeof. oversize from the screen-cloth and an opening. for discharge-of undersize which passes through the screen cloth onto the partition.

References. Cited; in the file ofthis patent; UNITED STATES PATENTS Number. Name Date l,.413,.612. Lowe Apn, 25-, 11922. 1-,459,.841. Mitchel1i Inne2'6, I923 2,284,671 Meinzer June: 2", 1942 

